add support for use as an ESM module

[davidbwaters]

All you would have to do is prepend export default to the main file and it would me much easier to use with npm managed projects. you could name it 'q5.esm.js' or something, but I would recommend pointing the package.json main filed to this version and it would work out of the box with node.

[s-rd]

I'm doing this currently (adding export default) with the min.js, but would be great to have this out of the box. +1